Something is definitely not right, wrong part something broken put together backwards. I have never done a '55 Ford but I've done hundreds of clutches at work, and they are all the same as far as the travel and pedal adjustment. When did this start. after a clutch was installed or was it working with the parts it has? Does the pedal have resistance without the return spring. Even with no return spring I don't think the pedal should be staying on the floor. The Mustangs had another big spring up under the dash besides the return spring down on the fork, not sure if yours had one of those. The one on the fork is mostly there just to keep the linkage up against the fork so it doesn't fall out of the fork.
Grab the fork at the trans and see how much travel it has. If you can, pry the fork back against the clutches' spring tension like the linkage was pushing on it, as far as it goes until it hit either hits the bellhousing or stops and see if its releasing, will the car roll in gear. If not the problem is inside the bellhousing and not your linkage. "DO NOT" try to start it in gear or it could take off on you if it's not releasing the clutch. Jack the rear wheels off the ground if you are going to do that. Parts can get bent, forks and Z-bars can break, clutch discs can be installed backwards. parts can be boxed wrong and sold to you. Never ever give up your original parts as cores until the project is done. You need them to compare to the new parts. You need them if something goes wrong to figure out what the problem is.
I had a Mustang break the fork pivot riveted to the bellhousing and the pedal went to the floor and stayed there, Had to drive it home with no clutch pedal, I had to start it in gear after stopping for red lights and shift it without the clutch, but you should have seen a broken fork of pivot when you pulled the trans. You can put a bore scope in the fork hole and see if you can see what's going on. They sale them dirt cheap, one that uses your phone as the screen, $30.00 an Amazon. I just had to do that on my daughters Scion TC. The clutch pedal felt fine, but it would not release absolutely would not go into gear. If I put it in gear with the clutch pedal down and started it, it lurched forward. It was gear all of the time. I was trying to figure out if it was the clutch hydraulics not pushing the fork far enough of somethiung else. I used a porta power to push the fork back all of the way until it hit the bellhousing, further than the pedal would have ever pushed it and the cluth was still engaged. Then I new it had to be something inside the bellhousing, 40-years of doping this and I never saw one break like this one. After 140,000 miles on the original clutch, one of the springs in the clutch disc came out and it got stuck between a flywheel bolt and the disc. The disc was always turning with the flywheel.
